The present invention relates to a device for aerating liquids or fluids, especially during flotation, and is embodied as a ring injector, in the housing of which, through which the fluid flows, there is disposed a middle piece that forms an annular channel with the housing, whereby at the level of the air discharge openings in the wall of the housing, the annular channel has its narrowest cross-sectional area; following this narrowest location of the annular channel in the direction of flow of the fluid, the annular channel undergoes a sudden increase in cross-sectional area, adjoining which a mixing and dispersing section leads to the outlet of the housing.
Devices of this type are known, and are used, for example, during flotation in order to separate the solid materials contained in a slurry from one another. The difficult-to-moisten solid particles are deposited on air bubbles that are generated in such devices, which are also known as gasifiers, injectors, or reactors. The solid material deposited on the air bubbles is generally discharged over the edge of the separating or flotation vessel.
With all aerating devices of this type it is desirable to keep the size of the air bubbles as small as possible, because this facilitates the deposition of solid particles during the flotation.
A device for mixing gases and liquids was already disclosed 50 years ago in U.S. Pat. No. 1,810,131. This device shows features of an aerating device such as was later disclosed (DE-OS No. 34 12 431) as a device for aerating dispersions, especially as a flotation device for delivering fibrous material suspensions or dispersions with a ring injector.
Air is supplied to the ring injector via air supply passages in the mixing section. As a result, the annular gap formed in the ring injector is aerated on the inside and the outside. The mixing section and the middle piece, which is centrally disposed within the mixing and dispersing section, are stepped, as a result of which, similar to a water-jet pump, the air is drawn into the inner and outer regions of the dispersion stream that is formed.
It is an object of the present invention to substantially improve devices of the aforementioned general type so that the specific energy consumption is reduced and the degree of selectively is increased.
This device should be especially suitable for the flotation of coal and other preparation material.